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1.

Two trains of equal length , running in opposite directions, pass a pole in 18 and 12 seconds. The trains will cross each other in -

  • A. 15.5 seconds
  • B. 15.5 seconds
  • C. 15.5 seconds
  • D. 15.5 seconds

Answer: Option D

Explanation:

Let the length of each train be x meter.
Then, speed of 1st train = x/18 m/sec
Speed of 2nd train = x/12 m/sec
Now,
When both trains cross each other, time taken
= 2x/(x/18 + x/12)
= 2x/{(2x + 3x)/36}
= (2x × 36)/5x
= 72/5
= 14.4seconds

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